There were two models of the HDT1000. 2388 and 2388s. The 2388 was built in 1982 and 1983. The 2388s in, probably 1984 and possibly 1985. That's speculation as I have found nothing that actually references the 2388s other than the fact that it's printed on the OOM and Parts Manuals. Other than on the front cover, the OOM never references the 2388s, and all illustrations are for the 2388. The parts manual is pretty much the same other than the fact that they tacked on a parts list for the PS as the last page of the manual. There are no footnotes indicating differences for parts between the 2388 and 2388s

For the 2388, other than the engine, the biggest would be factory Cruise Control, the longer hood, a different fuel tank, battery location, and a fishplate bolted to the front of the frame to support the fuel tank. I would assume that there would have been different cutouts in the frame to accommodate the engine. An engineering note does say "stronger frames".

For the 2388s, it appears that they added factory PS, an auxiliary hydro oil cooler, and different decals.

I gave Jerome a book that contained internal engineering notes from Bolens, and he found a reference to the HDT1000. On that sheet, they referred to it as the HT23D.

He was kind enough to send me a picture, which I'll attach here.

The biggest noticeable difference, other than the engine, is the travel speed The HDT1000 will zip along at 13 Mph! I'm assuming that Bolens did that because the folks overseas tend to drive their GTs on the road and they wanted a good speed for that.

Yours OB is a 2388S-01 That was built starting in 4-15-83 from what info I have found in the rest of that paper work. Those two books you still have dont happend to have more engineering changes do they? What you gave me starts at 225 I would think any number under 225 would have info on like on the tubes and large frames from the 60s because the were modal with number like 197 and 198.